Exception in thread "main" java.lang.NullPointerException in recursive linking

Asked Mar 09 '17 at 07:18

Active Mar 09 '17 at 07:18

Viewed 27 times

I'm a new one to use java. My problem may seem naive but I really don't know what to do. Here's the code:

class Employee{
    String name;

    Employee supervisor;
}

    public class EmployeeTest{
        public static void main(String[] args){
            Employee emp = new Employee();
            emp.name = "Xhaka";
            emp.supervisor.name = "Origi";
        if(emp.supervisor == null){
            System.out.println( emp.name + " is the boss and has no supervisor!" );
        }
        else{
            System.out.println("The supervisor of " + emp.name + " is " + emp.supervisor.name);
        }
    }

}

When I tried to compile it, it shows the problem with this:Exception in thread "main" java.lang.NullPointerException. How can I solve this question?

asked Mar 09 '17 at 07:18

Dao Zhou

1

Hint: `supervisor` is not initialized – Jens Mar 09 '17 at 07:20
@Jens How to initialize? I use Employee emp.supervisor = new Employee(); but it doesn't work. – Dao Zhou Mar 09 '17 at 07:56
There are many ways. in the employee constrauctror `this.Supervisor = new Employee` or in EmployeeTest emp.Supervisor = new Employee()`.... – Jens Mar 09 '17 at 07:58
BTW: Properties in a class should be private. `if(emp.supervisor == null){` makes no sence, because you have to inizialize `emp.supervisor` before this line and so `emp.supervisor´ can not be null here – Jens Mar 09 '17 at 07:58
@Jens Thank you so much! – Dao Zhou Mar 09 '17 at 08:00
You are welcome – Jens Mar 09 '17 at 08:00

Exception in thread "main" java.lang.NullPointerException in recursive linking

0 Answers0